Conductive seal ring for power bus distribution

ABSTRACT

A multi-block semiconductor device includes a first block and a second block operating in different power regimes from each other. A seal ring is around a periphery of the die, hermetically sealing the first and second blocks. The die has a substrate and an insulating layer, the seal ring being on the insulating layer. The seal ring serves as a power bus for the first block but not the second block. The seal ring and first block are electrically coupled to a first ground node, the first ground node being electrically isolated at a die-level from other ground nodes in the multi-block semiconductor device. In some embodiments, the second block is located in a central area of the die, and a plurality of metal lines electrically connect the seal ring to the first block, the metal lines being evenly spaced around a majority of the periphery of the semiconductor die.

BACKGROUND OF THE INVENTION

Radiofrequency (RF) devices that include analog or digital blocks on thesame die can suffer from cross talk between the separate blocks via acommon ground connection on the die. The cross talk from RF devices canbe particularly problematic for sensitive analog and digital circuitswhen they are located on the same die as the RF, because the RF sectionhandles relatively high power signals with relatively high frequencies.The high frequency of the signals allows them to pass more easilythrough reactive parasitic paths and disrupt signals in other blocks.

Seal rings are known in the art to provide stress relief and to providea seal to protect electrical components from environmental damage. Sealrings have also been used to address the problem of cross talk, which isa known phenomenon in integrated circuit design. For example, some sealrings in the art have been configured to be discontinuous to reducenoise coupling between digital circuits and RF circuits on an integratedcircuit chip. In other examples, the seal ring is coupled to a groundpotential to dissipate noise signals to ground, where the circuitcomponents are coupled to the seal ring. Further approaches to limit theeffect of cross talk include increasing the size of a layout orrearranging circuit blocks to increase the physical distance betweenseparate blocks.

SUMMARY

A multi-block semiconductor device includes a first block and a secondblock operating in different power regimes from each other. A seal ringis around a periphery of the die, hermetically sealing the first andsecond blocks. The die has a substrate and an insulating layer, the sealring being on the insulating layer. The seal ring serves as a power busfor the first block but not the second block. The seal ring and firstblock are electrically coupled to a first ground node, the first groundnode being electrically isolated at a die-level from other ground nodesin the multi-block semiconductor device. In some embodiments, the secondblock is located in a central area of the die, and a plurality of metallines electrically connect the seal ring to the first block, the metallines being evenly spaced around a majority of the periphery of thesemiconductor die.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a plan view of an integrated circuit with a seal ring asknown in the art.

FIG. 1B is a cross-sectional view of the seal ring of FIG. 1A.

FIG. 2A shows a plan view of a multi-block die with a seal ring, in oneembodiment.

FIG. 2B is a cross-sectional view of the seal ring of FIG. 2A.

FIG. 3 shows a plan view of a multi-block die with a seal ring, inanother embodiment.

FIG. 4 is a plan view of a multi-block die with a seal ring, in afurther embodiment in which the semiconductor die is packaged in a flipchip package.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1A-1B show an example of a prior art integrated circuit 100 havinga first circuit 110 and a second circuit 120, where, for example, firstcircuit 110 may be an analog circuit and second circuit 120 may be adigital circuit. The circuits 110 and 120 may also be referred to inthis disclosure as blocks. FIG. 1A shows a plan view, while FIG. 1Bshows a cross-sectional view of section A-A. In FIG. 1A, a seal ring 130surrounds the periphery of the integrated circuit 100, and the circuits110 and 120 are grounded to the seal ring 130 at a chip level throughthe ground connection 140. The integrated circuit 100 also includescontact metal pads 115 to enable external connections to RF circuit 110,contact metal pads 125 to enable external connections to digital circuit120, and a power supply terminal 150 for both RF circuit 110 and digitalcircuit 120.

FIG. 1B shows a cross-sectional view of the seal ring 130 at section A-Aof FIG. 1A. Seal ring 130 is formed on a substrate 160, and includes ametal layer 170, followed by a dielectric layer 180, another metal layer171, and another dielectric layer 181. A seal ring metal layer 175 isover dielectric layer 181, forming a top metal layer for the seal ring130. Metal layers 170, 171 and 175 are electrically connected by vias190 through the dielectric layers 180 and 181. Note that although onlytwo metal layers 170 and 171 and two dielectric layers 180 and 181 areshown between substrate 160 and seal ring metal layer 175 for clarity,additional layers may be present as needed for forming the circuitlayers of first circuit 110 and second circuit 120. The seal ring 130 isgrounded through ground terminal 140 of integrated circuit 100. It canbe grounded via the introduction of a chemical to the surface ofsubstrate 160 below the metal layer 170, such as a metal used to form asilicide with the substrate 160. In certain approaches, metal layer 170will be grounded to the substrate 160 through another layer of vias thatpierce through a layer of passivation or dielectric formed on thesurface of the substrate 160.

FIG. 2A shows a plan view of a multi-block semiconductor device in anembodiment of the present disclosure. An integrated circuit 200 has twoblocks, which shall be described as an RF circuit 210 and a digitalcircuit 220 in this embodiment. In other embodiments, one block could beoperating in an RF regime and multiple other blocks could be analogand/or digital circuitry associated with that RF circuitry. In moregeneral terms, the multi-block semiconductor device 200 has a firstblock 210 and a second block 220 operating in different power regimesfrom each other. In FIG. 2A, integrated circuit 200 also includes a sealring 230, ground terminals 240 and 241, power supply terminals 250 and251, contact metal pads 215 and 225, and metal lines 218. Power supplyterminal 250 provides the power for RF circuit 210, and contact metalpads 215 enable external connections to RF circuit 210. Power supplyterminal 251 provides the power for digital circuit 220, and contactmetal pads 225 enable external connections to digital circuit 220.

The blocks 210 and 220 operate in different power regimes, and each havetheir own ground nodes. Ground terminal 240 serves as the ground nodefor RF circuit 210, and ground terminal 241 serves as the ground nodefor digital circuit 220. Seal ring 230 extends around the periphery ofintegrated circuit 200, providing a hermetic seal and environmentalprotection for the device, and also serving as a crack-stop to preventcracks from spreading through the die and damaging the device. Thus,seal ring 230 hermetically seals the first block 210 and the secondblock 220. By using the same structure for two purposes, space on thedie is saved. Seal ring 230 connects to ground node 240 of RF circuitblock 210 in multi-block die 200. The seal ring 230 also serves as apower bus for the RF circuit 210, through metal lines 218 that connectblock 210 to the seal ring 230. Digital circuit 220, and any otherblocks other than RF circuit 210 in the multi-block die 200, are notelectrically connected to the seal ring 230. Thus, the seal ring 230serves as a power bus for the first block 210 but not for the secondblock 220. Also, digital circuit 220 is grounded to ground node 241,which is not grounded to seal ring 230. In other words, the blockswithin multi-block die 200 do not share a common ground at the chiplevel. The seal ring 230 and the first block 210 are electricallycoupled to first ground node 240, the first ground node 240 beingelectrically isolated at a die-level from other ground nodes (e.g.,ground node 241) in the multi-block semiconductor device 200. However,the blocks within multi-block semiconductor device 200 will generallyshare a common ground at the module level. Thus, RF circuit 210 has aseparate ground from other blocks on the same die, and noise coupling isreduced.

FIG. 2B shows a cross-sectional view of the seal ring 230 at section B-Bof FIG. 2A. The semiconductor die includes a substrate 260 and aninsulating layer 265, where insulating layer 265 may be a dielectricsuch as BPSG, TEOS, or FOX. The seal ring 230 may include a stack of oneor more metal layers. For example, in this embodiment the seal ring 230includes a metal layer 270 on insulating layer 265, followed by adielectric layer 280, another metal layer 271, and another dielectriclayer 281. A seal ring metal layer 275 is over dielectric layer 281,forming a top metal layer for the seal ring 230. The seal ring 230 mayalso include one or more vias between the metal layers. For example, inFIG. 2B, metal layers 270, 271 and 275 are electrically connected byvias 290 through the dielectric layers 280 and 281. Note that althoughonly two metal layers 270 and 271 and two dielectric layers 280 and 281are shown between insulating layer 265 and seal ring metal layer 275 forclarity, additional layers may be present as needed for forming thecircuit layers of RF circuit 210 and digital circuit 220. For example,the seal ring 230 can be a stack of all the metal layers and vias in theprocess used to form the die 200. The seal ring stack could also includea layer of silicon nitride over top metal layer 275 to create a smoothseal for the device. In some embodiments, the silicon nitride could bereplaced with any other passivation layer.

The seal ring 230 is grounded through ground terminal 240 of integratedcircuit 200 and through the metal layers 270, 271, and 275 as thoselayers can generally be provided to contact external terminals such asground node 240. Since the seal ring 230 is separated from substrate 260by insulating layer 265, transmission of noise from RF circuit 210through substrate 260 is reduced.

The seal ring 230 can also be used to route electrostatic discharge(ESD) currents. The seal ring may be configured to provide electrostaticdischarge protection to the first block by providing a path around thechip for ESD currents to flow from one die pin to another. One potentialdrawback to using separate grounds, such as ground terminals 240 and241, is that before the die is placed in a module, the device might bemore sensitive to ESD events. However, after the die is placed in amodule, the seal ring 230 can be used to provide ESD protection.

As mentioned above, the seal ring 230 also serves as a power bus for theblock 210, through metal lines 218. In the embodiment of FIG. 2A, themetal lines 218 are spaced around the portion of the die 200 thatencompasses RF circuit 210. In other embodiments, where RF circuit 210may be configured to span a larger area of the die 200, the metal lines218 may be spaced around the larger span of the RF circuit 210 toimprove power distribution. The cross-sectional width 232 of seal ring230 can be wider than conventional seal rings known in the art, toincrease the conductivity of the seal ring and thereby improve itsability to serve as a power bus. The increased width 232 of the sealring 230 does not limit its ability to serve as the basis for a hermeticseal, and improves its ability to serve as a crack-stop. The requiredwidth 232 for seal ring 230 to serve as a power bus depends on theapplication. For high frequency, high power applications, such as whenthe seal ring 230 serves as a power bus for an RF block, the seal ring“bus” can have a width 232 of, for example, 10 microns or wider, such as16 microns or more, or any width that provides sufficiently lowinductance so as not to cause significant radio frequency voltagepotential difference between seal ring contact points.

FIG. 3 shows another embodiment of a semiconductor die 300 having afirst circuit 310 and a second circuit 320, where second circuit 320 iscentrally located. Die 300 includes a substrate and an insulating layeras described for layers 260 and 265 in FIG. 2B above. First circuit 310may be an RF circuit, while second circuit 320 may be, for example, ananalog or digital circuit. Second circuit 320 is located approximatelyin a central area of the die, while RF circuit 310 is located around atleast a portion of the perimeter of second circuit 320. In more generalterms, the semiconductor device 300 has a first block 310 and a secondblock 320, the first block 310 and the second block 320 operating indifferent power regimes from each other. In the embodiment of FIG. 3,the second block 320 is located in a central area of the die 300. Thefirst block 310 at least partially surrounds the second block 320 inthis embodiment, such that the first block 310 spans at least two sidesof the second block 320. In FIG. 3, first circuit 310 forms a U-shapearound three edges of second circuit 320. In other embodiments, acentrally-located second circuit may have a first circuit that spans twoconsecutive edges, or two opposing edges, or surrounds the entireperimeter of the second circuit.

Seal ring 330 is located around a periphery of the die 300, andhermetically seals the first block 310 and the second block 320. Theseal ring 330 is on the insulating layer of the die 300, as describedabove in relation to FIG. 2B. Die 300 also includes a power supplyterminal 350 that supplies power to RF circuit 310. RF circuit 310 isgrounded through ground node 340, while second circuit 320 has aseparate ground node 341. The seal ring 330 and the first block 310 areelectrically coupled to first ground node 340, the first ground node 340being electrically isolated at a die-level from other ground nodes(e.g., ground node 341) in the multi-block semiconductor device 300. Insome embodiments, the first ground node 340 and the other ground nodesin the multi-block semiconductor device 300 share a common ground at amodule level.

In the embodiment of FIG. 3, seal ring 330 electrically connects to theRF circuit 310 through metal lines 318 that are evenly spaced around amajority of the periphery of the semiconductor die. Thus, seal ring 330serves as a power bus for the first block 310 but not for the secondblock 320. Also shown in this embodiment are metal contact pads 315around the periphery of the semiconductor die 300, where the metal lines318 are interspersed between the contact metal pads 315. This approachof interdigitating the seal ring's contact metal lines 318 with the RFcontact pads 315 makes for a more compact layout, and also helps inevenly distributing the power to RF circuit 310.

FIG. 4 shows yet another embodiment using a flip chip package approach.In FIG. 4, an integrated circuit 400 has an RF circuit 410 located atleast partially around a second circuit 420 similar the embodiment ofFIG. 3, where second circuit 420 is located approximately in the centerof the die. Second circuit 420 may be, for example, an analog or digitalcircuit. The second circuit 420 can be connected to flip-chip bumpcontact metal 425 located directly over the second circuit 420. RFcircuit 410 can likewise be connected to flip-chip bump contact metal415 directly over the RF circuit 410. A plurality of metal lines 418 arespaced around the periphery of RF circuit 410, which connect RF circuit410 to seal ring 430. Thus, seal ring 430 serves as a power bus for RFcircuit 410 but not for second circuit 420.

In further embodiments, the analog and digital circuitry may be locatedelsewhere on the die, such as not in the middle of the die, but withinthe die seal ring and not connected to the seal ring. In suchembodiments, the RF circuit would still connect to the die seal ringsuch that the seal ring serves as a power bus for the RF block but notthe other blocks.

The seal ring embodiments of the present disclosure can be used for anydesign that incorporates more than one desired power regime on a singlechip. However, it will provide the most benefit when very high isolationis desired between separate grounds in those different regimes. Anydesign using a transformer or balun on a die would fall under thisdefinition. For a specific example, wall wart transformer devices orwall wart AC to DC converters would benefit from this invention.

While the specification has been described in detail with respect tospecific embodiments of the invention, it will be appreciated that thoseskilled in the art, upon attaining an understanding of the foregoing,may readily conceive of alterations to, variations of, and equivalentsto these embodiments. These and other modifications and variations tothe present invention may be practiced by those of ordinary skill in theart, without departing from the scope of the present invention.Furthermore, those of ordinary skill in the art will appreciate that theforegoing description is by way of example only, and is not intended tolimit the invention. Thus, it is intended that the present subjectmatter covers such modifications and variations.

What is claimed is:
 1. A multi-block semiconductor device, comprising: asemiconductor die having a first block and a second block, the firstblock and the second block operating in different power regimes fromeach other, wherein the die comprises: a substrate; and an insulatinglayer; a seal ring on the insulating layer, the seal ring being around aperiphery of the die and hermetically sealing the first block and thesecond block, wherein the seal ring serves as a power bus for the firstblock but not for the second block; and a module into which thesemiconductor die is placed, further wherein the first block and thesecond block share a common ground at a level of the module; wherein theseal ring and the first block are electrically coupled to a first groundnode, the first ground node being electrically isolated at a die-levelfrom other ground nodes in the multi-block semiconductor device; furtherwherein the second block is located in a central area of the die and thefirst block at least partially surrounds the second block by forming aU-shape around the second block, and wherein the first block is disposedbetween the seal ring and at least two sides of the second block.
 2. Thedevice of claim 1, wherein the seal ring comprises a stack of aplurality of metal layers.
 3. The device of claim 2, wherein the sealring comprises a via between at least two of the metal layers.
 4. Thedevice of claim 1, wherein the seal ring has a cross-sectional width of10 microns or more.
 5. The device of claim 1, wherein the seal ring isconfigured to provide electrostatic discharge protection to the firstblock.
 6. The device of claim 1, wherein the first block comprises aradio frequency circuit.
 7. The device of claim 1, further comprisingmetal contact pads around the periphery of the semiconductor die,wherein a plurality of metal lines are interspersed between the metalcontact pads.
 8. The device of claim 1, wherein the semiconductor die ispackaged in a flip chip package.
 9. The device of claim 1, wherein theseal ring comprises a stack of a plurality of metal layers and a layerof silicon nitride over a topmost one of the metal layers.
 10. Amulti-block semiconductor device, comprising: a semiconductor die havinga first block and a second block, the first block and the second blockoperating in different power regimes from each other, the second blockbeing located in a central area of the die, wherein the die comprises: asubstrate; and an insulating layer; a seal ring around a periphery ofthe die and hermetically sealing the first block and the second block,the seal ring being on the insulating layer, wherein the seal ringserves as a power bus for the first block but not for the second block;a module into which the semiconductor die is placed, further wherein thefirst block and the second block share a common ground at a level of themodule; and a plurality of metal lines electrically connecting the sealring to the first block, the plurality of metal lines being evenlyspaced around a majority of the periphery of the semiconductor die;wherein the seal ring and the first block are electrically coupled to afirst ground node, the first ground node being electrically isolated ata die-level from other ground nodes in the multi-block semiconductordevice; further wherein the first block at least partially surrounds thesecond block by forming a U-shape around the second block, and whereinthe first block is disposed between the seal ring and at least two sidesof the second block.
 11. The device of claim 10, wherein the first blockcomprises a radio frequency circuit.
 12. The device of claim 10, whereinthe semiconductor die is packaged in a flip chip package.
 13. The deviceof claim 10, wherein the seal ring comprises a stack of a plurality ofmetal layers and a layer of silicon nitride over a topmost one of themetal layers.